Pineal gland

The conical-shaped pineal gland, or epiphysis cerebri, is attached by the pineal stalk to the roof of the diencephalon of the brain, from which it develops.  The gland is surrounded by a capsule of pia mater and arachnoid elements; connective tissue septa penetrate the gland, subdividing it into indistinct lobules.  The pineal secretes melatonin, which regulates circadian rhythms.  100x.

The conical-shaped pineal gland, or epiphysis cerebri, is attached by the pineal stalk to the roof of the diencephalon of the brain, from which it develops.  The gland is surrounded by a capsule of pia mater and arachnoid elements; connective tissue septa penetrate the gland, subdividing it into indistinct lobules.  The pineal secretes melatonin, which regulates circadian rhythms.  100x.

The conical-shaped pineal gland, or epiphysis cerebri, is attached by the pineal stalk to the roof of the diencephalon of the brain, from which it develops.  The gland is surrounded by a capsule of pia mater and arachnoid elements; connective tissue septa penetrate the gland, subdividing it into indistinct lobules.  The pineal secretes melatonin, which regulates circadian rhythms.  100x.

Corpora arenacea, or brain sand, are commonly found in the pineal gland.  These structures consist of accumulations of calcium phosphates and carbonates.  Because the pineal is a midline structure, these radio-opaque corpora arenacea are often used as indicators of midline deflection of the brain resulting from pathological conditions.

The major cell type of the pineal gland is the pinealocyte, a modified neuron.  The main secretory product of pinealocytes is melatonin, which regulates light-dark cycles (circadian rhythms).